Electromagnetic device and method of making



Sept. 13, 1960 R. HYINK ELECTROMAGNETIC DEVICE AND METHOD OF MAKINGFiled Nov. 28. 1956 2 Sheets-Sheet 1 ArzMA'ruQe TORG u:

Sept. 13, 1960 R. HYINK ELECTROMAGNETIC DEVICE AND METHOD OF MAKINGFiled NOV. 28. 1956 2 She ets-Sheet 2 MAGNETIC A l K GAP United StatesPatent ELECTROMAGNETIC DEVICE AND METHOD OF MAKING Roy Hyink, Milwaukee,Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation ofDelaware Filed Nov. 28, 1956, Ser. No. 624,919

9 Claims. (Cl. 317-165) This invention relates to improvements in andmethods of making electromagnetic devices.

While not limited thereto, the invention is especially applicable toalternating current electromagnetic contactors of the shading coil typeemployed in electrical control systems and the like.

It has heretofore been proposed to fill the window area of anelectromagnet with a coil, that is, to construct the core and energizingcoil so that the coil winding fills the interior space between thebottom of the core and the armature air gap and thus surrounds andextends throughout substantially the entire length of a pole piece.Providing a. core having a window area only large enough to accommodatethe required size of coil and then using a coil that occupies this fullspace has heretofore been thought to be necessary to afford anelectromagnet having optimum electrical characteristics. The pull curveof the aforementioned type of electromagnet has been known to bealterable by winding the coil with more than one size of wire to providea greater number of turns adjacent the air gap.

It has been found desirable to devise an electromagnetic device capableof selectively accommodating any one of a number of different sizes ofalternating current energizing coils. For some applications it isdesirable to employ direct current coils which inherently require agreater amount of copper in the coil for a given magnetic pull. It hasbeen discovered that a common size of the core constructed to receivethe maximum size of coil can be effectively employed to accommodate anyone of a plurality of different sizes of coils by properly positioningthe latter thereon. Spacing such coil into the area adjacent the air gapresults in a structure having optimum electrical characteristics.Concentration of the coil Winding in the area adjacent the air gap as inthe present invention not only permits use of selectively differentsizes of coils on a single size of core but also results in decrease ofthe leakage flux with a consequently higher percentage of the total fluxbridging the air gap to an extent that the total flux can be reducedwithout decreasing the open gap pull. This reduction in total requiredmagnetic flux affords pull characteristics which are more desirable formost applications and permits a significant reduction in the magnetizingvolt-amperes resulting in a substantial decrease in the powerconsumption. Consequently, the improved device operates at a lowertemperature although it has less heat radiating surface area thandevices heretofore known.

Accordingly, a primary object of the invention is to provide improvedmeans affording the aforementioned and other new results.

A more specific object of the invention is to provide an improvedelectromagnetic device capable of accommodating any one of a pluralityof selectively different sizes of energizing coils at optimumefiiciency.

A still more specific object of the invention is to provide improvedmeans for reducing the leakage flux in an ice electromagnetic device toan extent that the total flux can be reduced without decreasing the opengap pull.

Another specific object of the invention is to provide an improvedenergizing coil for such electromagnetic device which is simple inconstruction and economical to manufacture.

Another primary object of the invention is to provide a method ofimproving the efficiency and operating characteristics of anelectromagnetic device.

A further specific object of the invention is to provide a method ofmaking improved alternating current electromagnetic devices havingmaximum uniformity in their constituent parts.

Other objects and advantages of the invention will hereinafter appear.

While the device hereinafter described is effectively adapted to fulfillthe objects stated, it is to be understood that I do not intend toconfine my invention to the particular preferred embodiment ofelectromagnetic device disclosed, inasmuch as it is susceptible ofvarious modifications without departing from the scope of the appendedclaims.

In the accompanying drawings:

Figure 1 is a side view in elevation and partly in section of anelectromagnetic device constructed in accordance with the presentinvention;

Fig. 2 is a top view of the core assembly of the device taken along theline 22 of Fig. 1;

Fig. 3 is a top View of the armature of the device shown in Fig. 1; and

Fig. 4 graphically depicts operating characteristics of the device shownin Fig. 1.

Referring to Figs. 1 and 2 of the drawings, an electromagnetic deviceembodying the invention is designated generally by the numeral 10. Thedevice 10 has a U- shaped stationary frame portion or core 11 and amovable armature 12 shown in its normally open position. Surrounding oneleg of core 11 is a unitary coil structure 13 having a multiple-turnalternating current energizing winding 14 and a spacer 15 ofnon-magnetic material. Core 11 and energizing Winding 14 in combinationcomprise an electromagnetic which attracts armature 12 when winding 14is energized, and thereafter holds the armature in the closed positionas long as the electromagnet remains energized. Armature 12 ismechanically biased by one or more springs (not shown) or other suitablemeans which pull armature 12 away from pole faces 16a and 16b of core 11when the electromagnet is tie-energized. The pull of the electromagnetis of sufficient strength to overcome the opposing forces of theaforesaid springs and any load driven by the armature upon energizationof winding 14.

Core 11 as shown in Figs. 1 and 2 is constructed of a plurality of flatlaminations 18 of magnetic material such as silicon steel or the likeseparated by thin coatings or layers of electrical insulating material(not shown) in order to minimize eddy current losses in the core causedby the alternating magnetic flux. Pairs of recesses or slots 19a, 19band 20a, 2021 are provided on pole faces 16a and 16b, respectively, eachslot extending completely across the pole face in which it is locatedperpendicular to the laminations and the slots of each pair beinglocated symmetrically on opposite sides of the center of each pole face.Positioned in the respective pairs of slots 19a, 19b and 20a, 20b areshading coils 21a and 21b each of which is comprised of a single closedloop of electrically conducting material such as copper or the like.Each coil 21a and 21b surrounds the portion of the core leg adjacent toand associated with the portion of the pole face between the pair ofslots. The primary function of the shading coils is to afford anadditional component of magnetic flux developed by the current PatentedSept. 13, 1960 V induced in the shading coils which is displaced inphase relative to the phase of the flux developed by energizing winding14 to maintain the total of the absolute values of the fluxes above zerovalue at all times, thereby maintaining the armature pull above zerovalue. at all times to reducethe tendency of the armature to chatter dueto the cyclic variations of the alternating current. In the intermediatebottom portion of core 11 is an air gap 22 which may be filled, ifdesired, with a separator or spacer (not shown) of non-magnetic materialaffording a permanent gap in the magnetic path. Air gap 22 isperpendicular to the planes of laminations 18 and completely divides thecore into two laminated portions. The laminations of core 11 are heldtogether by generally U-shaped brackets 23 and 24 of non-magneticmaterial on opposite sides of the core and a plurality of rivets 25 orthe like extending through alined holes in the brackets and laminationsto form a unitary rigid structure. Brackets 23 and 24 comprise flanges26 and 27 laterally extending in opposite directions from the bottom ofeach respective U-shaped bracket forming a mounting structure for thecore assembly. Holes 26a and 27a are provided at spaced points in therespective flanges to facilitate securing the electromagnetic device toa stationary base. In addition each bracket has a longitudinal openingsuch as 28 shown in Fig. 1. adjacent each pole face and overlying eachpair of shading coil slots for accommodating the ends of the shadingcoils and retaining the latter in their respective pairs of slots. Ears29 and 30 are integrally formed on corresponding legs of brackets 23 and24 having alined holes therethrough for receiving an armature pivot pin31.

Armature 12 shown in Figs. 1 and 3 is similarly constructed of aplurality of flat laminations 32 of magnetic material such as siliconsteel or the like separated by thin coatings or layers of electricalinsulating material in order to minimize eddy current losses thereincaused by the alternating magnetic flux. The laminations of armature 12are held together by members 33 and 34 of magnetic material on oppositesides of the armature and a plurality of rivets 35 or the like extendingthrough alined holes in the members and laminations to form a unitaryrigid structure. Flanges 36 and 37 formed integrally with and extendinglaterally in opposite directions from the respective members 33 and 34are provided with one or more holes 33a and 33b for attaching forcetransmitting members such as contact actuators or the like (not shown)to the armature. Members 33 and 34 further comprise integrally formedpivot structures at corresponding ends thereof having linear portions33b, 34b and offset bent portions 330, 340 for removably receiving theopposite end portions of pivot pin 31. Portions 33c and 340 are formedto extend away from linear portions 33b and 34b at a suitable angle andto provide seats for pivot pin 31 such that members 33 and 34 are freeto move away from pivot pin 31 when the armature closes to aflordself-alining positive engagement between the respective sealingsurfaces.

Coil structure 13 having screw-threaded terminals 361; and 361) shown inFigs. 1 and 2 is comprised principally of the winding 14 and spacer 15.Washers 37a and 37b of electrical insulating material such as pressedboard or, the like are assembled on respectively opposite ends ofwinding 14, washer 37a separating winding 14 from spacer 15. Spacer 15has a dimension perpendicular to its axis equal to that of the smallestsize of coil em-' ployed. Thus, when spacer 15 is assembled to a coilhaving a larger dimension, an additional insulating member 38 may beemployed if desired to provide a structure of uniform width. Theaforementioned assembled parts including spacer 15 are then wrapped witha partially overlapping winding of tape 39 of electrically insulatingmaterial such as cotton or the like to provide a unitary coil structure.Coil structure 13 encircles. one.

leg of core 11 and the spacer end of the coil structure abuts theintermediate bottom portion of the core. Spacer 15 serves to maintainwinding 14 in the area immediately adjacent the air gap defined by poleface 16a and armature 12. The primary function of spacer 15 is toconcentrate the coil winding closer to the air gap to reduce the leakageflux which results in a higher percentage of the, total flux bridgingthe working air gap. As a result the total flux can be reduced withoutdecreasing the open gap pull with a consequent ,saving in weight andcost of the coil. Such reduction in the total required flux permits asignificant reduction in the sealed volt-amperes required for a givenpull resulting in a substantial decrease in the sealed watts consumed.Therefore, although the heat dissipating surface area of the coil isreduced, the device operates at a lower temperature because less heat isproduced. In addition, the single size of core accommodates a variety ofselectively different sizes of coil windings with their complementaryspacer elements resulting in substantial savings in manufacturing costs.

When coil winding 14 is energized, a magnetic field is developed in theair gaps between core 11 and armature 12 which acts to attract thelatter and overcome the restraining forces of the aforementioned biasingsprings. Currents induced in shading coils 21a and 21b develop phasedisplaced magnetic fluxes in the air gaps adjacent pole faces 16a and161), respectively, to maintain the total of the absolute values of thefluxes always above zero value. Armature- 12 is held in engagement withcore 11 as long as winding 14 is energized. Thus, a magnetic circuit isformed around the loop comprising core 11 and armature 12 having analternating magnetic flux oscillating at the frequency of thealternating current in winding 14. Magnetic circuits are also formed inloops through each respective shading coil and portions of thecorresponding core leg and armature sealing surface having a phasedisplaced alternating magnetic flux oscillating at the frequency of thealternating current in winding 14. When coil winding 14 is.de-energized, the armature returns to its normally open position.

Fig. 4, wherein sucwssive values of armature torque or pull are plottedagainst lengths of armature air gap or armature stroke to provide pullcurves for the electromagnetic device, graphically depicts theadvantageous results afforded by the present invention. Curves A and Ashow pull characteristics of prior electromagnetic devices atapproximately 100 percent and percent normal alternating current coilvoltage, respectively, while curves: B and B show pull characteristicsof the novel electromagnetic device employing a coil Winding fillingapproximately 60 percent of the window area at approximately percent and85 percent normal alternating current coil volt-age, respectively.Whilev the aforementioned curves depict approximate values of armaturepull throughout the armature stroke, it should be noted that at 100percent normal coil voltage the open air gap pull of the novelelectromagnetic device of the present invent-ion shown by curve B isequal to the open gap pull of prior devices shown by curve A down toapproximately point X. The present invention affords a reduction in themagnetizing volt-amperes of approxi. mately 40 percent and a reductionin the Wattage of approximately 30 percent with 60 cycle alternatingcurrent energization. Likewise, at 85 percent normal coil voltage theopen gap pull of the improved device shown by curve B is equal to theopen gap pull of heretofore known devices shovvn by curve A down toapproximately point Y.

In eleotromagnet devices heretofore known the sealed pull is inherentlytoo great and more than that which is required to maintain the armatureclosed even under severe shock conditions. This is. brought about by thelarge value of leakage flux rapidly decreasing as the armatureapproaches a sealed condition. The optimum pull curve for mostapplications is that which closely follows the load curve of the device.The load curve (not shown) of driven devices such as contactors and thelike falls below the pull curve A of prior electromagnetic devices asthe armature air gap approaches zero and more nearly follows curve B ofthe invention. Therefore, the excess energy provided by heretofore knowndevices and represented diagrammatically by the separation of curves Aand B from approximately point X toward zero air gap must be dissipatedas the armature strikes the core leg resulting in contact bounce andundesirable wear and noise.

On the other hand, electromagnetic devices constructed in accordancewith the present invention afford pull curves B and B having a moredesirable shape such that they follow the load curve of the drivendevice more closely in the region wherein the air gap approaches zerovalue. Therefore, correspondingly less excess energy is required to bedissipated as the armature seals with the consequent advantageousresults of less contact bounce, noise, wear and waste of energy.

I claim:

1. In an electromagnetic device having a. core for receiving any one ofa plurality of selectively dilferent sizes of energizing coils and anarmature mounted for movement relative to the core and normally biasedaway from the core to form an air gap therebetween, in combination, anenergizing coil surrounding at least a portion of the core, means forspacing said coil into the area adjacent the air gap, said meanscomprising a spacer member of non-magnetic material having aconfiguration substantially corresponding to the configuration of saidcoil, and means for securing said spacer member to one end of said coilto form a unitary structure.

2. In a device as claimed in claim 1, the last mentioned meanscomprising a partially overlapping winding of electrically insulatingtape surrounding said coil and said spacer member.

3. In an electromagnetic device having a generally U-shaped core forreceiving any one of a plurality of selectively different sizes ofenergizing coils and an armature pivoted for movement relative to thecore and normally biased away from the core to form an air gaptherebetween, in combination, a selected size of energizing coilsurrounding at least one leg of the core immediately adjacent the airgap, and non-magnetic means of complementary thickness filling the spacebetween the coil and the bottom of the U-shaped core to space andmaintain the coil in the aforementioned position.

4. In an alternating current electromagnetic device having a laminatedU-shaped core for accommodating any one of a plurality of selectivelydifferent sizes of energizing coils, a permanent non-magnetic gapbetween portions of the core and a laminated armature arranged formovement relative to the core and normally biased away from the latterto provide an air gap therebetween, in combination, means subjecting thearmature to an attractive force varying in the closing region of thearmature stroke substantially in proportion to the variation in theopposing load force which must be overcome to close the air gap, saidmeans comprising energizing coil means surrounding at least one leg ofthe U-shaped core and means for spacing said coil means from theintermediate portion of the core to concentrate said coil means adjacentthe air gap thereby to reduce the leakage flux.

5. In an alternating current electromagnetic device having a laminatedU-shaped core with a permanent nonmagnetic gap between portions of thelatter, a laminated armature normally biased away from the core toprovide an air gap therebetween, and an operating coil surrounding atleast one leg of the U-shaped core, the improvement comprising means forpositioning said coil adjacent the air gap and away from the bottom ofthe U-shaped core to introduce a greater percentage of the total fluxinto the air gap thereby to permit a reduction in the total flux withouta decrease in the open gap pull.

6. In a device as claimed in claim 5, the last mentioned meanscomprising a non-magnetic spacer member between the coil and the bottomof the U-shaped core and secured to the coil to form a unitary structuretherewith.

7. In combination, an energizing coil for an electromagnetic device forintroducing alternating magnetic flux into an air gap of the device andmeans for reducing the leakage flux so that a greater percentage of thetotal flux traverses the air gap, said means comprising a member ofsubstantial thickness for maintaining said coil immediately adjacent theair gap.

8. In an alternating current electromagnetic device having a core, anarmature normally biased away from the core to provide an air gaptherebetween, and a shading coil around at least a portion of the coreimmediately adjacent the air gap, in combination, an energizing coilsurrounding a portion of the core for developing an alternating magneticflux, and means for confining substantially all of the flux developed bysaid energizing coil to penetrate the air gap, said means comprisingnonmagnetic means spacing said energizing coil into an area immediatelyadjacent the shading coil.

9. A method of reducing the power consumption and operating temperatureof an alternating current electromagnetic device to the type having anenergizing coil extending over substantially the whole length of a polepiece without decreasing a given open gap attractive force on itsarmature, which method comprises the steps of substituting an energizingcoil productive of a smaller value of magnetic flux, and positioningsaid energizing coil adjacent the end of the pole piece defining the airgap to concentrate a greater percentage of the total flux in the airgap.

References Cited in the file of this patent UNITED STATES PATENTS1,258,813 Richmond Mar. 12, 1918 2,205,234 Armstrong et al. June 18,1940 2,546,740 Goldberg Mar. 27, 1951 2,558,640 Wurgler June 26, 19512,751,564 Marsh June 19, 1956

